1. Technical Field
The present invention relates to a process control method and a process control apparatus for semiconductor wafers or the like and, in particular, to a process control method and a process control apparatus at a process stage in which storage time between completion of pre-treatment and start of post-treatment is limited. More specifically, the invention relates to a process control method and a process control apparatus designed to achieve an efficient process flow and achieve an improvement in productivity by sequentially starting charging for a subsequent lot into the pre-treatment process, while controlling the starting point of charging on the basis of the starting point of post-treatment by post-treatment processing equipment, to eliminate excess products in-process over the time limit, when the storage time before starting the post-treatment process by the post-treatment processing equipment after completing the pre-treatment process by the pre-treatment processing equipment is limited.
2. Background Art
Hitherto, a well-known production system has been proposed, in which, upon completing a process for any product at a given stage, the product is transferred to a buffer for the next stage to start a new operation. For example, production control equipment which performs acceptance control and subsequent control of objects to be processed between stages in such a system was proposed in the Japanese Laid-opened Patent No. 8-179808. This prior art discloses production control equipment in which production control is conducted by the steps of: obtaining a list of operations undergone in the process previous to the current process to which an operation start request was given; requesting the previous process to start an operation in the order of priority if the previous process has a standby lot; inquiring of the previous process whether or not there are any available work resources; instructing the previous process to start a new operation if the work resources are available for the new operation; and requesting the previous process to supply the lot to the current process as early as possible.
Now, in the wafer processing of semiconductor devices, for example, a wet process (pre-treatment process) and a film formation process (post-treatment process) are conducted repeatedly for every mask, which is composed of ten through over twenty sheets. In the film formation process requiring particularly strict control of film formation accuracy, it is essential to strictly control the storage time of a semiconductor wafer from completion of the wet process to start of the film formation process. Because, if the storage time of semiconductor wafer is prolonged, dirt on the surface, metal contamination, organic material contamination, damaged layers or natural oxide layers on the surface, which were laboriously removed by the wet equipment, are reproduced on the surface of the wafer during storage of the wafers, and if a film formation process is applied to such a contaminated surface it is impossible to manufacture ICs having a predetermined quality.
As described above, if it is established that the storage time of a product from completion of the pre-treatment process to start of the post-treatment process should be within 4 hours, for example, it is necessary to start the post-treatment process within 4 hours. However, for example, since the process capacity of the film formation equipment (hereinafter also referred to as storage time observation processing equipment) during the post-treatment process varies depending on the passage of time. Therefore, if the treatment time using the film formation equipment is prolonged, the aforementioned conventional production control system cannot function sufficiently without holding excess products in-pending in the post-treatment process. Moreover, if the number of excess products in-process exceeds the processing capacity of the post-treatment equipment, the remaining products cannot start to undergo any treatment within the storage time observation period limit (hereinafter referred to as specified time) Tl (for example, 4 hours). Accordingly, a problem exists in that untreated products come out one after another over the specified time, and it is required to apply a re-treatment of the process to the lot (hereinafter referred to as product). On the other hand, if the post-treatment equipment does not have any excess product in-process, a next coming lot is charged into the post-treatment process by hastening the treatment of the lot capable of being treated in the previous process simultaneously with the start of the post-treatment process. Therefore, a further problem exists in that if any post-treatment equipment is low in its processing capacity and has a production bottleneck, the post-treatment process is not started and suspension of production continues until the subsequent lot is transferred to the post-treatment process, which further prolongs the overall treatment time through the entire system, eventually resulting in lowering of productivity.
The present invention was made to resolve the above-discussed problems and has an object of providing a process control method and a process control apparatus capable of achieving the most efficient process flow for post-treatment equipment having a bottleneck, and increasing productivity by eliminating any excess product in-process which requires re-treatment while taking balance of the process capacity for the post-treatment equipment into consideration to determine appropriately optimum number of products in-process so as not to exceed a specified time Tl.
To accomplish the foregoing object, the invention provides a process control method, for processing a plurality of lots including a preceding lot and a subsequent lot in a process stage comprising a hold stocker for holding each lot in a standby state, a pre-treatment processing equipment for pre-treating each lot brought out from said hold stocker on the basis of a standby release order, and a post-treatment processing equipment for post-treating each lot of which pre-treatment has completed, wherein a storage time for each lot between completion of pre-treatment in said pre-treatment processing equipment and start of post-treatment in said post-treatment processing equipment is limited, the process control method comprising: a step of establishing a standby time for the subsequent lot on the basis of the treatment starting time for the preceding lot in said post-treatment processing equipment so that completion time of the post-treatment for the preceding lot in said post-treatment processing equipment may substantially coincide with the starting time of the post-treatment for the subsequent lot in said post-treatment equipment; and a step of giving said standby order for the subsequent lot after elapsing the standby time utilizing the start of the treatment for the preceding lot in said post-treatment processing equipment as a trigger.
It is preferable that, in the process control method according to the invention, T1+Tw+T2 less than Td and Ta1=Tdxe2x88x92T1xe2x88x92Twxe2x88x92T2 are satisfied, supposing that the mentioned preceding lot is a first lot and the mentioned subsequent lot is a second lot to be treated subsequently, and establishing that a time obtained by adding a conveyance time from said hold stocker to said pre-treatment processing equipment to a waiting time until start of the pre-treatment is T1, a treatment time in the mentioned pre-treatment processing equipment is Tw, the storage time is T2, a treatment time in said post-treatment equipment is Td, and said standby time for each lot on and after the second lot is Ta1.
It is preferable that, in the process control method according to the invention, the second lot has a lot number subsequent to a lot number of the first lot.
It is preferable that, in the process control method according to the invention, T1+Tw+T2 greater than Td and Ta2=2xc3x97Tdxe2x88x92T1xe2x88x92Twxe2x88x92T2 are satisfied, supposing that the mentioned preceding lot is a first lot and the subsequent lots are second and third lots to be treated subsequently, and establishing that a time obtained by adding a conveyance time from said hold stocker to said pre-treatment processing equipment to a waiting time until start of pre-treatment is T1, a treatment time in the mentioned pre-treatment processing equipment is Tw, the storage time is T2, a treatment time in the mentioned post-treatment equipment is Td, and the standby time of each lot on and after the third lot is Ta1.
It is preferable that in the process control method according to the invention, the third lot has an alternate lot number to a lot number of the first lot.
The invention also provides a process control apparatus for processing a plurality of lots including a preceding lot and subsequent lot, comprising a hold stocker for holding each lot in a standby state, a pre-treatment processing equipment for pre-treating each lot brought out from said hold stocker on the basis of a standby release order, and a post-treatment processing equipment for post-treating each lot of which pre-treatment has completed, wherein a storage time for each lot between completion of pre-treatment in said pre-treatment processing equipment and start of post-treatment in said post-treatment equipment is limited,
the process control apparatus further comprises: an information storage section for storing information on a standby time for the subsequent lot on the basis of the starting time of the treatment of the preceding lot in said post-treatment processing equipment so that completion time of post-treatment of the preceding lot in said post-treatment processing equipment may substantially coincide with the starting time of post-treatment of the subsequent lot in said post-treatment processing equipment, information on the treatment starting time for the preceding lot in the said post-treatment processing equipment, and product request information for the subsequent lot; an FA computer including an arithmetic unit control section for calculating the standby time of the subsequent lot in accordance with an automatic program using said information on the standby time, said information on the treatment starting time, and said product request information, and for transmitting standby release order for the subsequent lot after elapsing the standby time; and an equipment control terminal which transfers said standby release order to said pre-treatment processing equipment.
It is preferable that, in the process control apparatus according to the invention, T1+Tw+T2 less than Td and Ta1=Tdxe2x88x92T1xe2x88x92Twxe2x88x92T2 are satisfied, supposing that the preceding lot is a first lot and the subsequent lot is a second lot to be treated subsequently, and establishing that a time obtained by adding a conveyance time from said hold stocker to said pre-treatment processing equipment to a waiting time until start of pre-treatment is T1, a treatment time in said pre-treatment processing equipment is Tw, the storage time is T2, a treatment time in said post-treatment equipment is Td, and said standby time of each lot on and after the second lot is Ta1.
It is preferable that, in the process control apparatus according to the invention, the second lot has a lot number subsequent to a lot number of the first lot.
It is preferable that, in the process control apparatus according to the invention, T1+Tw+T2 greater than Td and Ta2=2xc3x97Tdxe2x88x92T1xe2x88x92Twxe2x88x92T2 are satisfied, supposing that the preceding lot is a first lot and the subsequent lots are second and third lots to be treated subsequently, and establishing that a time obtained by adding a conveyance time from said hold stocker to said pre-treatment processing equipment to a waiting time until start of pre-treatment is T1, a treatment time in said pre-treatment processing equipment is Tw, the storage time is T2, a treatment time in said post-treatment processing equipment is Td, and said standby time of each lot on and after the third lot is Ta1.
It is preferable that, in the process control apparatus according to the invention, the third lot has an alternate lot number of a lot number of the first lot.
In the process control method and process control apparatus of above arrangement, following advantages are achieved.
Since in the process control method and the process control apparatus, the standby time for the subsequent lot is established on the basis of the treatment starting time of the preceding lot in said post-treatment processing equipment so that completion time of post-treatment for the preceding lot in said post-treatment processing equipment may almost coincide with the starting time of post-treatment for the subsequent lot in said post-treatment processing equipment, and the standby order given to the subsequent lot is released after elapsing the standby time utilizing the start of the treatment of the preceding lot as a trigger, it becomes possible to avoid re-treatment due to excess products in-process of which standby time has lapsed before the post-treatment process.
Further, in the process control method and the process control apparatus of above arrangement, the post-treatment processing equipment can be continuously and efficiently operated without any idle conditions and in addition. Since the time for keeping the lot, of which pre-treatment had been conducted using the pre-treatment processing equipment, in the storage period observation stage can be reduced, it becomes possible to produce products of high quality with high productivity.
Further, since the second lot has a lot number subsequent to the lot number of a fist lot which is a reference for establishing the standby time until charging the second lot, the invention performs the mentioned advantage particularly when the method and the apparatus are applied to the case wherein the treatment time in the post-treatment using the post-treatment processing equipment is longer than the required time from the release of the pending treatment to the start of charging into the pre-treatment processing equipment.
Furthermore, since the third lot has an alternate lot number to the lot number of the first lot which is a reference for establishing the standby time until charging the third lot, the invention performs the mentioned advantages particularly when the method and the apparatus are applied to the case wherein the time in the post-treatment using the post-treatment equipment is longer than the required time from the release of the pending treatment to the start of charging into the pre-treatment processing equipment.